[SPARK-29723][SQL] Get date and time parts of an interval as java classes

[MaxGekk]

What changes were proposed in this pull request?

I propose 2 new methods for CalendarInterval:

• extractAsPeriod() returns the date part of an interval as an instance of java.time.Period
• extractAsDuration() returns the time part of an interval as an instance of java.time.Duration

For example:

scala> import org.apache.spark.unsafe.types.CalendarInterval
scala> import java.time._
scala> val i = spark.sql("select interval 1 year 3 months 4 days 10 hours 30 seconds").collect()(0).getAs[CalendarInterval](0)
scala> LocalDate.of(2019, 11, 1).plus(i.period())
res8: java.time.LocalDate = 2021-02-05
scala> ZonedDateTime.parse("2019-11-01T12:13:14Z").plus(i.extractAsPeriod()).plus(i.extractAsDuration())
res9: java.time.ZonedDateTime = 2021-02-05T22:13:44Z

Why are the changes needed?

Taking into account that CalendarInterval has been already partially exposed to users via the collect operation, and probably it will be fully exposed in the future, it could be convenient for users to get the date and time parts of intervals as java classes:

• to avoid unnecessary dependency from Spark's classes in user code
• to easily use external libraries that accept standard Java classes.

Does this PR introduce any user-facing change?

No

How was this patch tested?

By new test in CalendarIntervalSuite.

[MaxGekk]

@cloud-fan @hvanhovell Please, take a look at this. If it makes sense for you, we could discuss alternative names for methods like getDatePart()/getTimePart() or extractDatePart/extractTimePart(), and etc.

[SparkQA]

Test build #113129 has finished for PR 26368 at commit cfb8b5a.

• This patch fails SparkR unit tests.
• This patch merges cleanly.
• This patch adds no public classes.

[MaxGekk]

jenkins, retest this, please

[SparkQA]

Test build #113156 has finished for PR 26368 at commit cfb8b5a.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[cloud-fan]

how about extractAsPeriod and extractAsDuration? We need to make it clear that CalendarInterval is a mix of Period and Duration.

[SparkQA]

Test build #113199 has finished for PR 26368 at commit 2f9f17a.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[dongjoon-hyun]

+1, LGTM. Thank you, @MaxGekk and @cloud-fan .
Merged to master.